We will continue to correlate alterations in the biochemical characteristics and macromolecular composition of cells during various crucial phases of the hepatocarcinogenic evolution. Our proposed studies will examine several aspects of the interaction of these carcinogenic agents with DNA and the resultant alterations in composition, structure and function. In brief, these studies will include the following: 1. We have now begun to purify and isolate a subspecies of DNA polymerase-alpha which appears during exposure of the rat liver to acetylaminofluorene. We will expand our purification procedure in order to determine if the infidelity of DNA replication demonstrated for this subspecies is the result of a contamination with cellular components or inherent as a result of mutation of the species or appearance of the new species. We will attempt to produce appropriate antibodies to the purified enzyme to enhance our ability to isolate it in sufficient quantities for further analysis. We will attempt to determine if similar altered enzymes appeared during other carcinogenic regimens. 2. We will examine the composition and structure of fractions of DNA produced by restriction endonuclease exposure. In particular, we will attempt to clone the J band previously described in order to obtain sufficient quantities for use in examination of mutational frequency or other aberrations induced during exposure to a carcinogen. We will also examine the methylation of these fractions in normal and malignant tissues. 3. We will continue to examine the integrity of DNA during carcinogenic evolution as determined by alkaline elution.